A wide variety of oilfield equipment uses seals to isolate zones of different pressure for a variety of different reasons. One common assembly that uses seals is known in the industry as an "on-off tool." An on-off tool has the capability of making a connection and selectively releasing the connection. It is frequently used in downhole applications to connect a tubing string to a packer or a crossover assembly. The on-off tool can connect and release in a variety of different ways. One way is a pin/slot combination involving a J-slot assembly, which allows the joint to be made up and released by a combination of rotational and longitudinal forces applied to the tubing string. Alternatively, a collet arrangement can be used, or hydraulic means can be employed for the make-up and release of the on-off tool.
In the past, operational problems have developed with seal assemblies that are put together downhole or at the surface. The physical action of the well fluid or gas acting on a portion of the joint before it is made up has, in the past, created a washing out effect which has displaced the sealing members from their mounted locations for sealing. Additionally, seals used in combination with metallic inserts have experienced insert flexing due to mechanical or thermal loads. When used in conjunction with close clearances, the desired sealing surface for the sealing elements has been scratched to the point where the sealing element is incapable of effective sealing. In an effort to counteract the possibility of marring the sealing surface due to deformations of the insert, attempts to use greater clearances between the components in the seal assembly when using the metallic inserts have created an additional concern over extrusion of the sealing elements from the insert.
Accordingly, the apparatus and method of the present invention have been developed to address the numerous needs of a sealing assembly, preferably those typically used in downhole applications. A nonmetallic insert has been developed to be used in combination with one or more bonded flexible seals in an assembly that addresses the potential problems experienced in the prior designs. The use of a softer material for the insert precludes the marring problem with the sealing surface. The softer insert material also has sufficient rigidity to assist as a back-up to the flexible bonded seals to greater limit the possibility of extrusion. Additional benefits are derived from the ease of manufacture and low cost of the sealing assembly of the present invention. The assembly can be used in a variety of applications in the oilfield and elsewhere, and is particularly suited to connections that must be made and released periodically where reliability of the seal is of utmost importance.